1. Field of the Invention
This invention concerns a cleaning device upon color-change in an electrostatic multi-color coating apparatus adapted to supply paints of a multiplicity of colors selectively under color-change to an electrostatic coating machine having an atomizing cup applied with a high voltage and rotationally driven at a high speed.
2. Description of the Prior Art
In an electrostatic multi-color coating apparatus for use in the coating of automobiles, the color of paint is often changed from one to another and cleaning for the inside of the coating apparatus is necessary on every color change for avoiding undesired mixing of colors. In such a case, it has been required to minimize the wasteful loss of paints upon color-change and to reduce the cleaning time upon color-change as short as possible.
In order to satisfy the foregoing requirements, it may be considered to situate a color-change device for selectively supplying paints of a multiplicity of colors near the electrostatic coating machine thereby shorten the paint supply channel connected between the coating machine and the color-change device so that the residual amount of paint in the paint supply channel is reduced.
However, if the color-change device is disposed near the coating machine, an excess load is undesirably applied to a reciprocator adapted to drive the coating machine in accordance with a predetermined coating pattern. In view of the above, the use of a considerably long paint supply channel has been inevitable.
Then, for shortening the cleaning time upon color-change, cleaning air and cleaning thinner at high pressure have been supplied from the color-change device to the paint supply channel to thereby rapidly clean the inside of the paint supply channel and the atomizing cup.
However, such a system involves another problem that the wasteful loss of the paint is inevitable and a great amount of paint and cleaning thinner are violently blown out from the cup of the electrostatic coating machine because a great amount of the cleaning thinner is supplied in a short time to the inside of the paint supply channel. They are overflown from and scattered around to the outside of the shroud disposed at the periphery of the cup of the coating machine for recovering the discharged liquid, to contaminate the peripheral equipments and the coating machine main body.
In order to suppress the wasteful loss of the paint, it has been proposed such a device in which a second color-change device smaller in size than the abovementioned color-change device is disposed near the electrostatic coating machine to shorten the paint supply channel connected between the second color-change device and the coating machine. Those paints used frequently, for example, white or red paint is selectively supplied from the second color-change device. For the cleaning upon color-change, cleaning air and cleaning thinner are alternately supplied from the second color-change device to the paint supply channel, the paint hose and the coating machine.
However, also in this case, if the cleaning air and the cleaning thinner at high pressure are supplied from the second color-change device, a great amount of paint is jetted out from the cup of the electrostatic coating machine, overflown from and scattered around to the outside of the shroud to contaminate the peripheral equipments or the coating machine main body, although the cleaning time can be shortened. Further, if the cleaning air and the cleaning thinner are supplied at low pressure from the second color change device in order to avoid this drawback, contamination occurs or paint color remains to the inside of a manifold disposed to the color-change device and having color-change valves, as well as to the inside of the paint supply channel connected therewith, whereby mixing of colors is resulted between paints used before and after the color-change to impair the quality of coating products.